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    SubjectRe: [PATCH v1 1/2] ata: libahci_platform: Get rid of dup message when IRQ can't be retrieved
    On Fri, Dec 10, 2021 at 07:38:40PM +0300, Sergey Shtylyov wrote:
    > On 12/10/21 11:47 AM, Andy Shevchenko wrote:
    >
    > >>> platform_get_irq() will print a message when it fails.
    > >>> No need to repeat this.
    > >>>
    > >>> While at it, drop redundant check for 0 as platform_get_irq() spills
    > >>> out a big WARN() in such case.
    > >>
    > >> The reason you should be able to remove the "if (!irq)" test is that
    > >> platform_get_irq() never returns 0. At least, that is what the function kdoc
    > >> says. But looking at platform_get_irq_optional(), which is called by
    > >> platform_get_irq(), the out label is:
    > >>
    > >> WARN(ret == 0, "0 is an invalid IRQ number\n");
    > >> return ret;
    > >>
    > >> So 0 will be returned as-is. That is rather weird. That should be fixed to
    > >> return -ENXIO:
    > >>
    > >> if (WARN(ret == 0, "0 is an invalid IRQ number\n"))
    > >> return -ENXIO;
    >
    > -ENXIO seems to me more fitting indeed (than -EINVAL that I used).
    >
    > >
    > > No, this is wrong for the same reasons I explained to Sergey.
    >
    > I fail to understand you, sorry. We're going in circles, it seems... :-/

    platform_get_irq_optional() is supposed to return 0 when there is no IRQ found,
    but everything else went alright.

    I'm tired to waste my time to go circles.

    Again, the problem is that platform_get_irq_optional() has wrong set of output
    values. And your patch doesn't fix that. And it has nothing to do with my code
    here.

    > > The problem is that this is _optional API and it has been misdesigned.
    > > Replacing things like above will increase the mess.
    >
    > What's wrong with replacing IRQ0 with -ENXIO now? platform_get_irq_optional()
    > (as in your patch) could then happily return 0 ISO -ENXIO. Contrarywise, if we don't
    > replace IRQ0 with -ENXIO, platform_get_irq_optional() will return 0 for both IRQ0
    > and missing IRQ! Am I clear enough? If you don't understand me now, I don't know what
    > to say... :-/

    See above. Read my messages again, please. I'm really tired to explain again
    and again the same.

    TL;DR: You simply try to "fix" in a correct place but in a wrong way.

    > >> return ret;
    > >>
    > >> Otherwise, I do not think that removing the "if (!irq)" hunk is safe. no ?
    > >
    > > No. This is not a business of the caller to workaround implementation
    > > details (bugs) of the core APIs.
    > > If something goes wrong, then it's platform_get_irq() to blame, and
    > > not the libahci_platform.
    >
    > I'm repeating myself already: we don't work around the bug in platform_get_irq(),

    Yes, you do.

    > we're working around the driver subsystems that treat 0 specially (and so don't
    > support IRQ0); libata treats 0 as an indication of the polling mode (moreover,
    > it will curse if you pass to it both IRQ == 0 and a pointer to an interrupt handler!
    > Am I clear enough this time? :-)

    Yes, and it doesn't contradict to what my patch does.
    Read comment against platform_get_irq(). If it returns 0,
    it's not a business of the callers to work around it.

    Am I clear enough this time? :-)

    --
    With Best Regards,
    Andy Shevchenko


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